javascript injected in tinymce editor by wordpress when gutenberg is desactivated - wordpress

Question

with a fresh install and up to date of wordpress (5.8.2), when I desactivate gutenberg editor, Wordpress add this javascript code in all TinyMCE editor (content, acf fields etc..)
I have no plugin and theme by default. I desactivate Gutenberg with code or with a plugin, no changes. Anyone have a tip ? thx
<script type="text/javascript">
var spector;
var captureOnLoad = false;
var captureOffScreen = false;
window.__SPECTOR_Canvases = [];
(function() {
var __SPECTOR_Origin_EXTENSION_GetContext = HTMLCanvasElement.prototype.getContext;
HTMLCanvasElement.prototype.__SPECTOR_Origin_EXTENSION_GetContext = __SPECTOR_Origin_EXTENSION_GetContext;
if (typeof OffscreenCanvas !== 'undefined') {
var __SPECTOR_Origin_EXTENSION_OffscreenGetContext = OffscreenCanvas.prototype.getContext;
OffscreenCanvas.prototype.__SPECTOR_Origin_EXTENSION_OffscreenGetContext = __SPECTOR_Origin_EXTENSION_OffscreenGetContext;
OffscreenCanvas.prototype.getContext = function () {
var context = null;
if (!arguments.length) {
return context;
}
if (arguments.length === 1) {
context = this.__SPECTOR_Origin_EXTENSION_OffscreenGetContext(arguments[0]);
if (context === null) {
return context;
}
}
else if (arguments.length === 2) {
context = this.__SPECTOR_Origin_EXTENSION_OffscreenGetContext(arguments[0], arguments[1]);
if (context === null) {
return context;
}
}
var contextNames = ["webgl", "experimental-webgl", "webgl2", "experimental-webgl2"];
if (contextNames.indexOf(arguments[0]) !== -1) {
// context.canvas.setAttribute("__spector_context_type", arguments[0]);
// Notify the page a canvas is available.
var myEvent = new CustomEvent("SpectorWebGLCanvasAvailableEvent");
document.dispatchEvent(myEvent);
this.id = "Offscreen";
window.__SPECTOR_Canvases.push(this);
if (captureOnLoad) {
// Ensures canvas is in the dom to capture the one we are currently tracking.
if (false) {
spector.captureContext(context, 500, false, false);
captureOnLoad = false;
}
}
}
return context;
}
}
HTMLCanvasElement.prototype.getContext = function () {
var context = null;
if (!arguments.length) {
return context;
}
if (arguments.length === 1) {
context = this.__SPECTOR_Origin_EXTENSION_GetContext(arguments[0]);
if (context === null) {
return context;
}
}
else if (arguments.length === 2) {
context = this.__SPECTOR_Origin_EXTENSION_GetContext(arguments[0], arguments[1]);
if (context === null) {
return context;
}
}
var contextNames = ["webgl", "experimental-webgl", "webgl2", "experimental-webgl2"];
if (contextNames.indexOf(arguments[0]) !== -1) {
context.canvas.setAttribute("__spector_context_type", arguments[0]);
// Notify the page a canvas is available.
var myEvent = new CustomEvent("SpectorWebGLCanvasAvailableEvent");
document.dispatchEvent(myEvent);
if (captureOffScreen) {
var found = false;
for (var i = 0; i < window.__SPECTOR_Canvases.length; i++) {
if (window.__SPECTOR_Canvases[i] === this) {
found = true;
break;
}
}
if (!found) {
window.__SPECTOR_Canvases.push(this);
}
}
if (captureOnLoad) {
// Ensures canvas is in the dom to capture the one we are currently tracking.
if (this.parentElement || false) {
spector.captureContext(context, 500, false, false);
captureOnLoad = false;
}
}
}
return context;
}
})()</script>

Answer 1

It is very likely added by the Spector.js extension : same behaviour with the Spector extension enabled on Firefox (when switching editor, or after save) => disabling the extension solved the issue.